linux-kernel - Re: [RFC] clk: vc5: Add bindings for output configurations

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Message-ID: <20200405012847.GA5234@bogus>
Date:   Sat, 4 Apr 2020 19:28:47 -0600
From:   Rob Herring <robh@...nel.org>
To:     Adam Ford <aford173@...il.com>
Cc:     devicetree@...r.kernel.org, aford@...conembedded.com,
        charles.stevens@...icpd.com,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, linux-clk@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC] clk: vc5: Add bindings for output configurations

On Thu, Mar 26, 2020 at 04:32:51PM -0500, Adam Ford wrote:
> The Versaclock can be purchased in a non-programmed configuration.
> If that is the case, the driver needs to configure the chip to
> output the correct signal type, voltage and slew.
> 
> This RFC is proposing an additional binding to allow non-programmed
> chips to be configured beyond their default configuration.
> 
> Signed-off-by: Adam Ford <aford173@...il.com>
> 
> diff --git a/Documentation/devicetree/bindings/clock/idt,versaclock5.txt b/Documentation/devicetree/bindings/clock/idt,versaclock5.txt
> index 05a245c9df08..4bc46ed9ba4a 100644
> --- a/Documentation/devicetree/bindings/clock/idt,versaclock5.txt
> +++ b/Documentation/devicetree/bindings/clock/idt,versaclock5.txt
> @@ -30,6 +30,25 @@ Required properties:
>  		- 5p49v5933 and
>  		- 5p49v5935: (optional) property not present or "clkin".
>  
> +For all output ports, an option child node can be used to specify:
> +
> +- mode: can be one of
> +		  - LVPECL: Low-voltage positive/psuedo emitter-coupled logic
> +		  - CMOS
> +		  - HCSL 
> +		  - LVDS: Low voltage differential signal
> +
> +- voltage-level:  can be one of the following microvolts
> +		  - 1800000
> +		  - 2500000
> +		  - 3300000
> +-  slew: Percent of normal, can be one of 
> +		  - P80 
> +		  - P85
> +		  - P90
> +		  - P100 
> +
> +
>  ==Mapping between clock specifier and physical pins==
>  
>  When referencing the provided clock in the DT using phandle and
> @@ -62,6 +81,8 @@ clock specifier, the following mapping applies:
>  
>  ==Example==
>  
> +#include <dt-bindings/versaclock.h>
> +
>  /* 25MHz reference crystal */
>  ref25: ref25m {
>  	compatible = "fixed-clock";
> @@ -80,6 +101,13 @@ i2c-master-node {
>  		/* Connect XIN input to 25MHz reference */
>  		clocks = <&ref25m>;
>  		clock-names = "xin";
> +
> +		ports@1 {

'ports' is already taken as a node name.

> +			reg = <1>;

What do the reg value signify?

> +			mode = <CMOS>;
> +			pwr_sel = <1800000>;

Not documented. Don't use '-' in property names.

> +			slew = <P80>;
> +		};
>  	};
>  };
>  
> -- 
> 2.25.1
>